Effect of Seed Roasting on Canolol, Tocopherol, and Phospholipid

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Effect of seed roasting on canolol, tocopherol, phospholipid content, Maillard type reactions and oxidative stability of mustard and rapeseed oils Kshitij Shrestha, and Bruno De Meulenaer J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/jf500549t • Publication Date (Web): 02 Jun 2014 Downloaded from http://pubs.acs.org on June 8, 2014

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Journal of Agricultural and Food Chemistry

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Effect of seed roasting on canolol, tocopherol,

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phospholipid content, Maillard type reactions and

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oxidative stability of mustard and rapeseed oils

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Kshitij Shrestha1 and Bruno De Meulenaer*1

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1

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Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium

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*

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NutriFOODchem unit - Department of Food Safety and Food Quality (partner in

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Food2Know)

NutriFOODchem Unit, Department of Food Safety and Food Quality, Faculty of Bioscience

Corresponding author: Prof. dr. ir. Bruno De Meulenaer

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Faculty of Bioscience Engineering

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Ghent University, Coupure links 653

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B-9000, Ghent

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Belgium

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Email: [email protected]

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Tel: + 32 9 264 61 66; Fax: + 32 9 264 62 15

16 17

Funding: Special Research Fund - BOF, Ghent University

1

ACS Paragon Plus Environment


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Abstract

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This study was carried out to study the effect of roasting on different compositional

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parameters and oil oxidative stability of three Brassica species (B. juncea (BJ), B. juncea var.

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oriental (BJO) and B. napus (rapeseed, RS)). After 10 min of roasting at 165 oC, canolol

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content of BJ, BJO and RS oil reached 297.8, 171.6 and 808.5 µg/g and, the phospholipid

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phosphorus content reached 453.6, 342.6 and 224.2 µg/g oil, respectively. The BJ and BJO

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seed showed more prominent browning reactions than RS, due to the presence of higher

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amounts of reducing sugars, lysine, arginine; and the occurrence of Maillard type browning

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reactions of phospholipids. The UV-visible spectra, fluorescence and pyrrole content showed

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the presence of browning reaction products in the roasted seed oils. Roasting increased the

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oxidative stability of all the varieties. Canolol formation could only partially explain for such

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observation. Other roasting effects such as phospholipids extraction, Maillard type browning

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reaction products etc were also responsible for that.

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Keywords: 2,6-dimethoxy-4-vinylphenol (canolol), mustard, rapeseed, lipid oxidation, seed

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roasting, phospholipid browning, Maillard type reactions

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Introduction

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Seed roasting has been known to increase the oil oxidative stability of different seeds, such as

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mustard (1), sesame (2), Pistacia terebinthus (3), pine nut (4), cashew (5), perilla (6), apricot

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(7), pumpkin (8, 9), walnut (10), rapeseed (RS) (11) etc. However, there are considerable

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differences in the manner roasting improves the oil oxidative stability of these seeds. For

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instance, production of different radical scavengers, such as sesamol in sesame seed (2) and

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canolol in RS (11-14) during seed roasting are considered to play an important role for such

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phenomenon. In some cases, increased phospholipid extraction after seed roasting has also

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been suggested (6, 9). In most of the cases, Maillard browning reactions between amino acids

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and reducing sugars have been proposed as an important contributing factor for such

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observation (1, 3-5, 8, 10, 11). These results suggest that roasting can have different effects in

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different types of seeds. Hence, it is important to understand the roasting effects and the

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manner it improves the oil oxidative stability on each type of seed, separately.

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Mustard seeds are generally roasted before oil extraction, and the crude oil extracted using a

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screw expeller, is consumed without refining in different south Asian countries such as India

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and Nepal (1, 15). The traditional mustard and RS varieties contain high amounts of erucic

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acid, while various low erucic RS varieties have also been developed by breeding practices

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(14). Although a number of seed roasting experiments have been reported for RS (11, 12) and

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mustard varieties (1, 11), a clear insight and in-depth understanding of how roasting improves

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oxidative stability of these varieties are still lacking. For instance, all these studies consider

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Maillard reactions to be partially responsible for increasing the oxidative stability of roasted

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seed oil; however, none of them clearly demonstrates the occurrence of such reactions by

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evaluating the loss of reducing sugars and amino acids, and by analyzing the browning 3



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reaction markers in the roasted seed oil. Moreover, the formation of canolol and its

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contribution on the oxidative stability has been completely ignored in roasting experiments

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carried out on high erucic mustard seed oil (1). Recently however, canolol formation during

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roasting has also been confirmed in those varieties (14). Furthermore, most of the previous

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studies have ignored the possibility of Maillard type browning reactions involving the amino

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group containing phospholipid (e.g. phosphatidylethanolamine (PE)). Such browning reaction

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products have been demonstrated to be more lipophilic compared to Maillard reaction

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products between amino acids and reducing sugars (16). Hence, they are more likely to be

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extracted with oil, and can contribute its antioxidative activity (17, 18). A correlation study

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considering the effect of all these different factors on the oxidative stability of roasted

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mustard seed oil has been published recently (18). It has provided a novel insight that the

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presence of radical scavengers (such as canolol and tocopherol) could not solely explain the

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very high oxidative stability of roasted mustard seed oil. Such observation has been shown to

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be primarily linked with phospholipid content and the presence of lipophilic Maillard type

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browning reaction products, in addition to canolol that is formed during roasting (18).

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However, that study was carried out on roasted mustard seed oils collected from the market;

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and hence, it does not clearly demonstrate how such antioxidative compounds are generated

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during seed roasting and if there exist the difference in the roasting effect among different

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mustard and RS varieties.

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Therefore, the current study has been carried out to evaluate the seed roasting effect on

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different compositional parameters and oil oxidative stability of different Brassica species.

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The three species selected for the study were Brassica juncea (Indian mustard), Brassica

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juncea var. oriental (oriental mustard) and Brassica napus (European rapeseed).

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Materials and methods

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Materials and Reagents

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The seeds of two high erucic acid mustard varieties (Brassica juncea (BJ) and Brassica

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juncea var. oriental (BJO)) and a low erucic acid rapeseed (RS) variety (B. napus) were

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collected from the local market of Ghent, Belgium. Tocopherol standard was obtained from

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DSM (New Jersey, USA). Syringaldehyde and 1,2-dioleoyl-sn-glycero-3-

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phosphoethanolamine were purchased from Sigma Aldrich (Steinheim, Germany).

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Nonadecanoic acid was purchased from Fluka (Switzerland). The HPLC grade hexane was

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bought from VWR International (Leuven, Belgium). Other reagents and solvents were of

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analytical grade and obtained from reliable commercial sources.

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Synthesis of canolol

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Canolol was synthesized from syringaldehyde by condensation with malonic acid and then

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double decarboxylation under microwave condition as described previously (14). The

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ultraviolet, fluorescence, liquid chromatography-mass spectrometry and nuclear magnetic

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resonance spectra were used to confirm the identity and purity of the synthesized compound

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(14). The synthesized canolol was used as a standard for quantification.

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Analytical methods

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Fatty acid methyl esters were prepared using the boron trifluoride method (American Oil

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Chemists Society, 1990) and were analyzed on a gas chromatograph using the method

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described previously (18). Nonadecanoic acid was used as an internal standard for the

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quantification. 5



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The analysis of the total amino acid profile of seed sample was carried out using the

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previously described procedure (19) and included a full hydrolysis of the sample in acidic

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conditions and a liquid chromatographic analysis using fluorescence detection after

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derivatization. Thus tryptophan and cysteine were lost and glutamine and asparagine were

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converted to glutamic and aspartic acid respectively. Tryptophan was separately analyzed

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after basic hydrolysis followed by similar chromatographic conditions. The analysis of the

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free amino acid content was carried out after their extraction from the ground seeds with 15

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% trichloroacetic acid followed by similar chromatographic analysis, without acid hydrolysis.

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Sarcosine was used as an internal standard to quantify proline. Norvaline was used as an

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internal standard to quantify other amino acids.

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Analysis of sugar content in the seed sample was carried out gas chromatographically after

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aqueous extraction of the sugar and derivatisation via oximation and silylation using the

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previously described procedure (20). Phenyl-β-D-glucopyranoside was used as an internal

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standard for the quantification.

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Tocopherol and canolol content of the oils were analyzed in a high pressure liquid

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chromatograph using a fluorescence detector, after separation in a silica column as described

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previously (14).

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Peroxide value (PV) of oil was determined by using an iron based spectrophotometric method

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(21). Calibration curve was constructed using a standard iron (III) chloride solution as

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described in the same method. Calibration was done using six concentrations in duplicate in

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the range of 5 to 30 µg of iron (III). The multiple R-squared value was more than 0.99 for the

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calibration. Such calibration curve was constructed just before the measurement of the

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peroxide value of the samples. 6


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Phospholipid phosphorus content of oil was analyzed spectrophotometrically after the

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formation of a phospholipid phosphorus-molybdate complex as described before (18).

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The pyrrolized phospholipid content of the oil samples was analyzed using a previously

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described procedure (22). The absorbance of the Ehrlich adducts was measured at 512 nm

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and the blank absorbance without Ehrlich reagent was subtracted during calculation. The

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reported value of extinction coefficient of Ehrilich adducts (153000 M-1 cm-1) with 1-[1-(2-

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hydroxyethyl)-1H-pyrrol-2-yl]propan-1-ol was used in the calculation (22).

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UV-visible absorbance spectra of the oil solution in iso-octane (25 mg/mL) was measured

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using a Cary 50 UV/Vis spectrophotometer (Varian) in a quartz cuvette. Fluorescence

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(excitation at 350 nm and emission at 440 nm) of the same oil solution was additionally

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measured using a Spectramax Gemini XS fluorescence spectrophotometer as described

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previously (18). Fluorescence is expressed as the percentage fluorescence of 1 µM quinine

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sulphate solution in 0.1 M H2SO4.

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Experimental setup

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Mustard and rapeseed were roasted in a beaker, which was dipped inside an oil bath

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maintained at 180 oC as reported earlier (14). Briefly, 80 g seed sample was added to a heated

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beaker placed on the oil bath (180 oC). The seed sample and heating oil were continuously

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agitated with two electric mechanical stirrers. The temperature of seed sample and heating oil

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was continuously monitored using Testo thermostat proves. The oil temperature was

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maintained constant at 180 oC and seed roasting was carried out for 10, 20, 30, 45, 60 and 90

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min. The seed temperature profile with time followed the equation T = 32.796 ln (t) + 89.422

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(R2 = 0.99) for the first 10 min of roasting, where T is the seed temperature (oC) and t is the

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roasting time (min). Afterwards, seed temperature remained constant at 165 ± 3 oC.

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The roasted and unroasted seeds were ground. The total amino acid profile was analyzed on

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unroasted seed powder. The reducing sugar content and free amino acid profile was analyzed

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both on unroasted and 10 min roasted seed powder.

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The oil was extracted from unroasted and roasted seeds using petroleum ether (14).

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Tocopherol, canolol, phospholipid and browning reaction markers (absorbance, fluorescence

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and pyrrolized phospholipid content) were analyzed on unroasted and roasted seed oils. The

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extracted oil (750 µL) was kept in a 1.5 mL loosely capped HPLC glass vial and stored at 104

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o

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at different time intervals. Both roasting and oxidation studies were carried out in

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independent triplicate experiments.

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Statistical analysis

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All data are presented as mean values ± 95% confidence interval of mean based on three

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independent experiments, unless otherwise stated. The logarithmic transformations of the

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different data was done, whenever necessary, to have homoscedasticity before carrying out

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the statistical analysis. ANOVA and post-hoc Tukey test were performed using TIBCO

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Spotfire S+ 8.1 software. The significance level is p < 0.05, unless otherwise indicated.

C in order to accelerate the oxidation process. Oil oxidation was monitored by analyzing PV

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Results and discussion

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Effect of roasting on different compositional parameters

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Mustard and rapeseed roasting are known to form canolol by decarboxylation of sinapic acid

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(11, 12, 14, 23, 24). Roasting of seed before oil extraction increased the canolol content of oil

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in all the varieties (Table 1). The maximum canolol content of oil was reached during 10 to

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20 min of seed roasting. Oil from 20 min roasted RS contained the highest amount of canolol,

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which was 2.8 times higher compared to BJ seed oil and 4.9 times higher compared to BJO

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seed oil, roasted for same time. Higher canolol formation in roasted RS compared to different

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mustard seed varieties was also reported previously (14). Roasting for more than 20 min

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gradually reduced the canolol content in all the varieties. The decrease in the canolol content

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during longer roasting time was also reported previously (24). The canolol content of the

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roasted rapeseed oil was reported in a similar range previously (23, 24).

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The tocopherol content of the unroasted and roasted seed oil of different varieties is given in

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Table 1. The α-tocopherol content in the unroasted RS oil was more than double the amount

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present in both unroasted mustard seed oils. It remained stable during RS roasting, while a

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significant gradual degradation was observed for both BJ and BJO mustard varieties. The γ-

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tocopherol content in all the three varieties was quite comparable. Its degradation was

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observed in all the varieties during 10 min of roasting. Afterwards, it remained constant in

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RS, while slight degradation was observed during BJO roasting. The BJ seed oil showed a

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gradual and the largest degradation in γ-tocopherol during longer roasting. The

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plastochromanol-8 content remained relatively stable in the BJ seed oil during roasting. On

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the other hand, a significant increment was observed in the BJO and RS oil during the first 10

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min of roasting. The disruption of matrix during roasting could be responsible for the

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increased extractability. Longer roasting time had little effect in all the varieties studied.

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The phospholipid phosphorus content of the unroasted seed oils, extracted using petroleum

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ether, was in the range of 8 to 30 µg/g oil (Table 1). On the other hand, when the same

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unroasted seed powder was extracted with a chloroform/methanol solvent mixture (2:1, v/v);

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the phospholipid phosphorus content was 500 to 600 µg/g oil. Therefore, the lower

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phospholipid content of unroasted seed oil was due to the poor extractability with petroleum

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ether from the unroasted seed matrix. Roasting for 10 min significantly increased the oil

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phospholipid content for all the varieties. This observation was similar to the increased

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extractability of plastochromanol-8 after seed roasting. The increased phospholipid content of

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the oil after seed roasting was also reported previously (9). Roasting for more than 10 min

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showed a gradual decrease in the phospholipid phosphorus content in the oil of all the

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varieties. The decrease in extractability could indicate its chemical modifications, for

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instance, they could be covalently bound to matrix compounds.

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Maillard reaction is one of the most well known nonenzymatic browning reactions in heat

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treated food products. The possibility for such reactions during seed roasting was studied by

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evaluating the changes in the amino acids and reducing sugars content. Among the free

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amino acids, RS contained a significantly higher quantity of glutamate, histidine, alanine,

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valine, isoleucine and lysine compared to both BJ and BJO mustard varieties (Table 2). On

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the other hand, both BJ and BJO mustard varieties contained significantly higher quantity of

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free arginine compared to RS. After 10 min of roasting, more than 85% of free amino acids

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were lost, indicating the occurrence of Maillard reaction in all the varieties. The loss of

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individual amino acid was quite comparable in all the varieties. Therefore, the formation of 10


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low molecular weight antioxidative compounds from such reactions could also be

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comparable among those varieties. On the other hand, the total amino acids content (in fat

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free dry matter (FFDM) basis) was higher in mustard varieties compared to that in RS (Table

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3). Particularly notable were the presence of 30 to 40% higher arginine and 14 to 16% higher

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lysine in mustard varieties compared to that in RS. Because of the presence of free amino

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group, these amino acids are particularly responsible for the Maillard reactions involving

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proteins. The formation of high molecular weight hydrophilic antioxidative compounds from

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such reactions could be much more pronounced in mustard varieties compared to that in RS.

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The effect of seed roasting on the sugar content was additionally evaluated in all the varieties

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(Table 4). Both mustard varieties contained significantly higher quantity of glucose and

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lower quantity of sucrose compared to RS before roasting. The fructose content of BJ

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mustard seed was also higher compared to both BJO seed and RS. After 10 min of roasting,

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the glucose content decreased significantly in all the varieties compared to the amount

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present in the unroasted seed. The loss of glucose was around 4 times higher in both mustard

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varieties compared to that in rapeseed. Moreover, the sucrose content of both mustard

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varieties also decreased significantly, likely due to its hydrolysis into glucose and fructose.

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The increase in sucrose content in rapeseed after seed roasting could possibly due to its

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formation via the hydrolysis of stachyose and raffinose present in the matrix (25).

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The ground seed meal of different varieties before and after 20 min roasting has been shown

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in Figure 1. This picture illustrates that browning reactions during roasting were more

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pronounced in mustard varieties compared to that in RS. This could be linked with the

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presence of higher quantities of both reducing sugars and reactive amino acids (e.g. lysine,

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arginine) in mustard varieties compared to that in RS.

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In addition to amino acids, the amino group containing phospholipid (e.g. PE) are also known

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to take part in the Maillard type browning reactions with reducing sugars (17). Both types of

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browning reactions could be expected to happen simultaneously in the seed however, their

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extraction in the oil could be affected by their polarity differences. In a previous study, it was

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shown that the amino group of PE was even more reactive with ribose than that of lysine

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(16). These authors reported that, when the aqueous reaction mixture of PE, ribose and lysine

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was extracted with chloroform/methanol (2:1, v/v) to have phase separation, the brown

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compounds due to PE/ribose and lysine/ribose got separated into the organic and aqueous

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phase, respectively (16). These observations showed that the lysine/ribose Maillard reaction

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products are more hydrophilic, while the PE/ribose reaction system could produce lipophilic

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Maillard type reaction products. The same extraction method was used to characterize the

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brown compounds in the roasted seed oil. It was observed that the major brown compounds

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of oil remained in the organic phase indicating that these brown compounds could be mainly

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due to phospholipids browning compared to the reducing sugar amino acid Maillard reactions.

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The possibility of such phospholipid browning reaction products was also reported previously

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based on the high correlation observed between the phospholipid content, absorbance,

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fluorescence and the pyrrolized phospholipid content in roasted mustard seed oil (18).

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The changes in the browning reaction markers in the oil after seed roasting of different

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varieties were further evaluated (Table 1). The absorbance of oil at 350 nm gradually

251

increased during roasting in all the varieties. The choice of this marker is based on the recent

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report that oxidative stability of the roasted mustard seed oil is highly correlated at this

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wavelength (18). The BJ seed oil showed the highest increment in the absorbance and

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reached a maximum after 20 min of roasting, which was more than 3 times compared to that

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of RS oil and more than 2 times compared to BJO seed oil, roasted for the same time. After 12


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45 min of roasting, the absorbance values of all the varieties remained almost constant. The

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absorbance value after 45 min was comparable between BJ and BJO seed oil, and was around

258

double the amount compared to that of RS oil. To illustrate that more clearly, the changes in

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the UV-visible absorbance spectra of oil after roasting for 10 and 90 min for all the varieties

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are shown in Figure 2. It shows that the increase in the UV-visible absorbance due to

261

browning reactions within the 10 min of roasting was highest in BJ followed by BJO and

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rapeseed oil. After 90 min of roasting, BJ and BJO seed oil showed similar UV-visible

263

absorbance spectra. On the other hand, the UV-visible absorbance spectra of roasted rapeseed

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oil (even after 90 min of roasting) was lower than that of 10 min roasted BJ oil. This showed

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that browning reactions were more prominent in BJ and BJO mustard varieties compared to

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that in rapeseed variety. In addition, roasting increased the oil fluorescence (excitation 350

267

nm and emission 440 nm) in all the varieties (Table 1). However, fluorescence development

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was comparable in all the varieties and could not differentiate the extent of browning

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observed with the absorbance at 350 nm. Furthermore, the presence of the Maillard type

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browning reaction products in the roasted seed oil was supported by the increment in the

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pyrrolized phospholipid content after seed roasting in all the varieties (Table 1).

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Oxidative stability of roasted seed oil of different varieties

273

The fatty acid compositions of all the oils are given in Table 5. Both mustard varieties were

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rich in erucic acid, while the RS was rich in oleic acid. However, total saturated,

275

monounsaturated and polyunsaturated fatty acids content were comparable in all the varieties.

276

The oxidative stability of unroasted seed oil and roasted seed oil was evaluated by monitoring

277

the changes in the PV during accelerated oxidation at 104 oC (Figure 3). The previous study

278

showed that roasted mustard seed oil could have a very high oxidative stability with induction 13



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period more than 60 days during storage at 50 oC (18). Therefore, higher storage temperature

280

(104 oC) was chosen to accelerate the oxidation. The vials were loosely capped so as to

281

maintain the constant atmospheric oxygen concentration in the headspace. The experiment is

282

similar to the active oxygen method used for the evaluation of oxidative stability of oil at 100

283

o

284

peroxides could degrade at this temperature and the oil oxidation could be different from the

285

autoxidation, however, such effects could be similar in the oil samples with similar fatty acid

286

composition. Therefore, the results from this experiments should be taken as the relative

287

oxidative stability among the samples with similar fatty acid composition during accelerated

288

oxidation.

289

Roasting for 10 min significantly improved the oxidative stability of all the varieties

290

compared to their respective unroasted seed oil (Figure 3). Such increment in the oxidative

291

stability due to roasting was more prominent in BJ and BJO varieties compared to that in RS

292

variety. Roasting for longer time had a smaller additional effect.

293

Canolol is a potent antioxidant and is known to play an important role in the oxidative

294

stability of roasted rapeseed oil (11, 12). However, other factors in addition to canolol could

295

also be responsible for the increased oxidative stability. To evaluate the role of canolol alone,

296

oxidative stability was evaluated after the addition of canolol to the unroasted seed oil

297

equivalent to the amounts formed after 10 min roasting (Figure 2). In addition, oxidative

298

stability of unroasted rapeseed oil containing canolol equivalent to the amount in 10 min

299

roasted BJ seed oil was also evaluated. Canolol addition to the unroasted mustard seed (BJ

300

and BJO) could not increase their oxidative stability, while it showed significant protective

301

role in the rapeseed oil. In all the varieties, 10 min roasted seed oil was more stable compared

302

to their respective unroasted seed oil added with equivalent quantity of canolol. These

C by saturating the oil with oxygen, and monitoring the PV during storage. It is known that

14


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observation showed that canolol could play a significant role in increasing the oxidative

304

stability of roasted RS oil, however its formation alone could not be responsible for the

305

increased oxidative stability after seed roasting. Furthermore, even though BJ and BJO

306

varieties showed smaller increment in canolol during roasting compared to that in RS,

307

increment in the oxidative stability after roasting was more prominent in BJ and BJO

308

varieties compared to that in RS. This could be linked with other multiple effects of seed

309

roasting such as increased extraction of phospholipid, formation of antioxidants via Maillard

310

type reactions etc. Such roasting effects depend on the chemical composition of the seeds,

311

which could be different in the different varieties. In the current example, BJ and BJO

312

mustard seed showed stronger Maillard type browning reactions compared to RS variety.

313

Maillard type browning reaction products are known to have strong antioxidative activity (17,

314

26). Such browning reaction products could be responsible for the increased oxidative

315

stability of roasted mustard (BJ and BJO) seed oil in addition to the canolol formed during

316

the roasting. Further studies are required to isolate and identify the antioxidative compounds

317

formed during such reactions that can be used as a natural antioxidants in different food

318

products.

319

Abbreviations: PV peroxide value, BJ Brassica juncea, BJO B. juncea var. oriental, PE

320

phosphatidylethanolamine, RS rapeseed, FFDM fat free dry matter

321

ACKNOWLEDGEMENT

322

The study was financially supported by Special Research Fund - BOF, Ghent University,

323

which is gratefully acknowledged.

324

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5. Chandrasekara, N.; Shahidi, F. Oxidative Stability of Cashew Oils from Raw and Roasted Nuts. J. Am. Oil Chem. Soc. 2011, 88 (8), 1197-1202.

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6. Zhao, T.; Hong, S. I.; Lee, J.; Lee, J. S.; Kim, I. H. Impact of Roasting on the Chemical Composition and Oxidative Stability of Perilla Oil. Journal of Food Science 2012, 77 (12), C1273-C1278.

344 345 346

7. Durmaz, G.; Karabulut, I.; Topcu, A.; Asilturk, M.; Kutlu, T. Roasting-Related Changes in Oxidative Stability and Antioxidant Capacity of Apricot Kernel Oil. J. Am. Oil Chem. Soc. 2010, 87 (4), 401-409.

347 348 349

8. Nederal, S.; Skevin, D.; Kraljic, K.; Obranovic, M.; Papesa, S.; Bataljaku, A. Chemical Composition and Oxidative Stability of Roasted and Cold Pressed Pumpkin Seed Oils. J. Am. Oil Chem. Soc. 2012, 89 (9), 1763-1770.

350 351 352

9. Vujasinovic, V.; Djilas, S.; Dimic, E.; Basic, Z.; Radocaj, O. The effect of roasting on the chemical composition and oxidative stability of pumpkin oil. Eur. J. Lipid Sci. Technol. 2012, 114 (5), 568-574.

353 354 355

10. Vaidya, B.; Eun, J. B. Effect of roasting on oxidative and tocopherol stability of walnut oil during storage in the dark. Eur. J. Lipid Sci. Technol. 2013, 115 (3), 348-355.

356 357 358

11. Wijesundera, C.; Ceccato, C.; Fagan, P.; Shen, Z. Seed roasting improves the oxidative stability of canola (B. napus) and mustard (B. juncea) seed oils. Eur. J. Lipid Sci. Technol. 2008, 110 (4), 360-367.

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359 360 361

12. Koski, A.; Pekkarinen, S.; Hopia, A.; Wähälä, K.; Heinonen, M. Processing of rapeseed oil: effects on sinapic acid derivative content and oxidative stability. European Food Research and Technology 2003, 217 (2), 110-114.

362 363 364 365

13. Matthaus, B. Effect of Canolol on Oxidation of Edible Oils. In Canola and Rapeseed: Production, Processing, Food Quality, and Nutrition, Thiyam, U.; Eskin, M.; Mattaus, B., Eds.; CRC Press, Taylor & Francis Group: Boca Raton, 2012; pp 317-328.

366 367 368 369

14. Shrestha, K.; Stevens, C. V.; De Meulenaer, B. Isolation and identification of a potent radical scavenger (canolol) from roasted high erucic mustard seed oil from Nepal and its formation during roasting. J. Agric. Food Chem. 2012, 60 (30), 7506-7512.

370 371 372

15. Vaidya, B.; Choe, E. Stability of tocopherols and lutein in oil extracted from roasted or unroasted mustard seeds during the oil oxidation in the dark. Food Science and Biotechnology 2011, 20 (1), 193-199.

373 374 375

16. Zamora, R.; Nogales, F.; Hidalgo, F. J. Phospholipid oxidation and nonenzymatic browning development in phosphatidylethanolamine/ribose/lysine model systems. European Food Research and Technology 2005, 220 (5), 459-465.

376 377 378 379

17. Zamora, R.; León, M. M.; Hidalgo, F. J. Free radical-scavenging activity of nonenzymatically-browned phospholipids produced in the reaction between phosphatidylethanolamine and ribose in hydrophobic media. Food Chemistry 2011, 124 (4), 1490-1495.

380 381 382 383

18. Shrestha, K.; Gemechu, F. G.; De Meulenaer, B. A novel insight on the high oxidative stability of roasted mustard seed oil in relation to phospholipid, Maillard type reaction products, tocopherol and canolol content. Food Research International 2013, 54 (1), 587-594.

384 385 386

19. Kerkaert, B.; Mestdagh, F.; Cucu, T.; Shrestha, K.; Camp, J.; Meulenaer, B. The impact of photo-induced molecular changes of dairy proteins on their ACEinhibitory peptides and activity. Amino Acids 2012, 43 (2), 951-962.

387 388 389 390

20. De Wilde, T.; De Meulenaer, B.; Mestdagh, F.; Govaert, Y.; Vandeburie, S.; Ooghe, W.; Fraselle, S.; Demeulemeester, K.; Van Peteghem, C.; Calus, A.; Degroodt, J. M.; Verhe, R. Influence of Storage Practices on Acrylamide Formation during Potato Frying. J. Agric. Food Chem. 2005, 53 (16), 6550-6557.

391 392 393

21. Shantha, N. C.; Decker, E. A. Rapid, sensitive, iron-based spectrophotometric methods for determination of peroxide values of food lipids. J AOAC Int 1994, 77 (2), 421-424.

394 395 396

22. Zamora, R.; Olmo, C.; Navarro, J. L.; Hidalgo, F. J. Contribution of phospholipid pyrrolization to the color reversion produced during deodorization of poorly degummed vegetable oils. J. Agric. Food Chem. 2004, 52 (13), 4166-4171. 17



Page 18 of 28

397 398 399 400

23. Wakamatsu, D.; Morimura, S.; Sawa, T.; Kida, K.; Nakai, C.; Maeda, H. Isolation, identification, and structure of potent alkyl-peroxyl radical scavenger in crude canola oil, canolol. Bioscience, Biotechnology and Biochemistry 2005, 69 (8), 1568-1574.

401 402

24. Spielmeyer, A.; Wagner, A.; Jahreis, G. Influence of thermal treatment of rapeseed on the canolol content. Food Chemistry 2009, 112 (4), 944-948.

403 404

25. Shahidi, F. Canola and Rapeseed: production, chemistry, nutrition and processing technology; Van Nostrand Reinhold: New York, 1990.

405 406 407

26. Shrestha, K.; De Meulenaer, B. Antioxidant activity of Maillard type reaction products between phosphatidylethanolamine and glucose. Food Chemistry 2014, 161, 8-15.

408 409

18


Page 19 of 28


Figure captions Figure 1. Mustard (BJ and BJO) and rapeseed meal before and after 20 min of roasting Figure 2. Changes in the visible spectrum of the oil after roasting of B. juncea (A), B. juncea var oriental (B) and B. napus (rapeseed) (C) Figure 3. Changes in the PV of unroasted seed oil, roasted seed oil and canolol added unroasted seed oil of different varieties stored at 104 oC (

0 h,

9 h,

32 h and

98 h)

19



Page 20 of 28

Figure 1.

20


Page 21 of 28


Figure 2. 1.0

A

0.9 0.8

BJ 0

absorbance

0.7 BJ 10

0.6

BJ 90

0.5 0.4 0.3 0.2 0.1 0.0 300

350

400

450

500

550

wavelength (nm) 1.0

B

0.9 0.8

BJO 0

absorbance

0.7 BJO 10

0.6

BJO 90

0.5 0.4 0.3 0.2 0.1 0.0 300

350

400

450

500

550

wavelength (nm) 1.0

C

0.9 0.8

RS 0

absorbance

0.7 RS 10

0.6

RS 90

0.5 0.4 0.3 0.2 0.1 0.0 300

350

400

450

500

550

wavelength (nm)

21


ACS Paragon Plus Environment RS_roasted 90 min

RS_roasted 60 min

RS_roasted 45 min

RS_roasted 30 min

RS_roasted 20 min

RS_roasted 10 min

RS_unroasted + canolol 800 µg/g

RS_unroasted + canolol 300 µg/g

RS_unroasted

BJO_roasted 90 min

BJO_roasted 60 min

BJO_roasted 45 min

BJO_roasted 30 min

BJO_roasted 20 min

BJO_roasted 10 min

BJO_unroasted + canolol 170 µg/g

BJO_unroasted

BJ_roasted 90 min

BJ_roasted 60 min

BJ_roasted 45 min

BJ_roasted 30 min

BJ_roasted 20 min

BJ_roasted 10 min

BJ_unroasted + canolol 300 µg/g

BJ_unroasted

Peroxide value (meq oxygen/kg oil)

Journal of Agricultural and Food Chemistry Page 22 of 28

Figure 3.

50

45

40

35

30

25

20

15

10

5

0

22

Page 23 of 28


Tables Table 1. Effect of seed roasting on different compositional parameters and browning reaction markers of extracted oil variety

roasting time (min)

canolol (µg/g oil)

α-tocopherol (µg/g oil)

γ-tocopherol (µg/g oil)

plastochromanol8 (µg/g oil)

phospholipid phosphorus (µg/g)

absorbance (350 nm)

fluorescence1 (ex. 350 nm, em 440 nm)

pyrrole content (nmol/g)

BJ

unroasted

5.41 ± 0.01 a

89.56 ± 2.39 def

290.34 ± 2.36 hi

39.59 ± 1.43 hij

8.66 ± 1.81 a

0.03 ± 0.01 a

3.65 ± 0.19 a

6.97 ± 1.68 ab

BJ

10

297.76 ± 6.26 e

80.57 ± 0.99 cde

266.84 ± 2.16 efg

39.15 ± 0.81 hi

453.62 ± 51.65 k

0.56 ± 0.03 ghi

64.43 ± 1.34 efg

54.97 ± 4.64 c

BJ

20

301.19 ± 5.31 e

76.92 ± 2.02 cd

244.61 ± 17.93 d

38.16 ± 4.20 hi

319.23 ± 46.62 ijk

0.91 ± 0.13 k

56.71 ± 3.54 de

75.32 ± 6.87 efgh

BJ

30

255.31 ± 5.93 d

71.58 ± 1.89 bc

224.28 ± 3.79 c

36.63 ± 0.22 gh

175.54 ± 49.39 efgh

0.63 ± 0.02 hij

57.76 ± 3.19 de

86.45 ± 6.41 hi

BJ

45

234.56 ± 9.14 d

61.41 ± 5.57 b

221.74 ± 1.44 c

36.77 ± 0.69 hi

133.52 ± 35.91 def

0.63 ± 0.10 hij

64.57 ± 2.72 efg

65.04 ± 3.85 cde

BJ

60

181.82 ± 0.63 c

22.49 ± 1.81 a

200.09 ± 1.19 b

36.89 ± 0.60 hi

110.72 ± 30.13 de

0.70 ± 0.03 ij

71.34 ± 0.72 fghi

65.16 ± 4.43 cde

BJ

90

146.84 ± 12.39 b

12.96 ± 5.08 a

177.95 ± 11.47 a

32.99 ± 1.93 fg

117.74 ± 5.62 def

0.69 ± 0.01 ij

78.00 ± 2.73 ij

91.97 ± 5.66 ij

BJO

unroasted

5.06 ± 0.15 a

97.99 ± 0.82 f

358.49 ± 4.97 j

9.26 ± 0.25 b

15.66 ± 3.72 b

0.03 ± 0.01 a

3.51 ± 0.09 a

4.31 ± 1.50 a

BJO

10

171.64 ± 3.20 bc

89.72 ± 4.69 ef

295.40 ± 10.29 i

26.71 ± 0.88 c

342.57 ± 31.71 jk

0.26 ± 0.03 bc

42.72 ± 3.02 c

81.58 ± 2.44 fghi

BJO

20

174.32 ± 4.02 bc

87.30 ± 1.19 def

293.50 ± 1.57 i

27.61 ± 0.31 cd

271.75 ± 21.58 hijk

0.39 ± 0.02 cdef

43.62 ± 1.61 c

91.88 ± 2.05 ij

BJO

30

163.20 ± 1.25 bc

86.86 ± 0.58 def

291.26 ± 4.59 hi

29.50 ± 1.30 cdef

198.72 ± 21.46 fghi

0.52 ± 0.01 fgh

55.31 ± 1.87 d

89.02 ± 4.11 hi

BJO

45

154.23 ± 1.79 bc

85.65 ± 1.42 def

288.36 ± 4.23 hi

29.10 ± 1.13 cde

167.58 ± 46.28 efgh

0.65 ± 0.00 hij

67.41 ± 0.68 fgh

84.74 ± 2.36 ghi

BJO

60

157.98 ± 2.82 bc

85.42 ± 0.81 de

288.22 ± 2.06 hi

31.10 ± 0.14 def

128.29 ± 5.95 def

0.67 ± 0.00 ij

75.07 ± 2.51 hi

89.77 ± 0.89 hij

BJO

90

146.70 ± 0.49 b

76.61 ± 3.22 cd

283.36 ± 2.45 ghi

31.70 ± 0.80 ef

137.81 ± 41.53 defg

0.77 ± 0.09 jk

85.32 ± 1.73 j

172.31 ± 1.26 k

RS

unroasted

5.19 ± 0.09 a

214.89 ± 4.33 g

274.15 ± 3.81 fgh

1.80 ± 0.09 a

30.45 ± 9.38 c

0.04 ± 0.01 a

12.71 ± 0.28 b

1.92 ± 1.47 a

RS

10

808.48 ± 24.67 i

218.93 ± 14.31 gh

255.05 ± 14.61 de

40.29 ± 2.42 ij

224.15 ± 11.16 ghij

0.23 ± 0.09 b

68.90 ± 5.18 fgh

18.94 ± 9.64 b

RS

20

847.13 ± 22.30 j

222.79 ± 5.62 gh

258.10 ± 5.30 def

43.73 ± 0.77 jk

164.66 ± 19.28 efgh

0.27 ± 0.02 bcd

71.03 ± 1.17 fghi

60.12 ± 14.33 cd

RS

30

809.06 ± 4.22 i

224.49 ± 2.47 gh

260.62 ± 2.85 def

46.26 ± 0.98 kl

188.26 ± 47.47 fgh

0.45 ± 0.08 efg

68.96 ± 1.74 fgh

77.34 ± 1.56 efgh

RS

45

760.45 ± 31.19 h

229.81 ± 3.20 h

261.48 ± 2.61 def

48.01 ± 1.02 l

151.87 ± 12.68 efg

0.41 ± 0.02 defg

67.97 ± 0.71 fgh

71.36 ± 2.36 defg

RS

60

708.26 ± 15.97 g

225.77 ± 4.96 gh

257.19 ± 4.42 de

46.37 ± 0.58 kl

147.60 ± 39.54 defg

0.32 ± 0.11 bcde

63.54 ± 9.07 def

68.62 ± 5.30 cdef

RS

90

650.17 ± 13.83 f

227.06 ± 4.60 gh

257.06 ± 5.65 de

47.06 ± 1.14 kl

88.12 ± 4.96 d

0.36 ± 0.08 bcde

72.17 ± 3.00 ghi

102.20 ± 5.46 j

1

expressed as % of fluorescence of quinine sulphate solution (1 µM in 0.1 M H2SO4)

Values with different letters in a same column are significantly different (p < 0.05)

23



Page 24 of 28

Table 2. Free amino acids content (mg/100 g FFDM) of seeds before and after 10 min of roasting of different varieties BJ (unroasted)

BJO (unroasted)

RS (unroasted)

BJ (roasted 10 min)

BJO (roasted 10 min)

RS (roasted 10 min)

Aspartate

51.72 ± 1.12 d

92.18 ± 0.32 f

85.81 ± 1.74 e

10.23 ± 1.95 a

17.91 ± 0.93 b

25.96 ± 3.06 c

Glutamate

269.00 ± 3.35 b

259.75 ± 4.49 b

304.92 ± 8.12 c

15.11 ± 2.81 a

13.93 ± 0.64 a

23.19 ± 3.82 a

Asparagine

175.12 ± 1.93 e

100.69 ± 0.56 c

145.21 ± 4.04 d

17.76 ± 3.26 b

10.11 ± 0.68 a

21.64 ± 3.09 b

Serine

19.75 ± 1.34 c

42.58 ± 3.55 d

15.34 ± 2.95 c

4.46 ± 0.88 ab

8.88 ± 0.09 b

2.96 ± 0.32 a

Glutamine

6.99 ± 0.16 b

1.92 ± 3.75 a

7.54 ± 0.78 b

0.43 ± 0.07 a

0.36 ± 0.00 a

0.48 ± 0.15 a

Amino acids

Histidine

8.20 ± 0.25 b

9.52 ± 0.64 c

12.13 ± 0.47 d

1.59 ± 0.39 a

1.56 ± 0.14 a

1.58 ± 0.07 a

Glycine

6.35 ± 1.56 bc

12.23 ± 2.50 d

10.17 ± 2.56 cd

1.90 ± 0.37 a

2.99 ± 0.02 ab

3.04 ± 0.18 ab

Threonine

5.68 ± 0.15 b

8.90 ± 0.46 d

6.80 ± 0.32 c

0.91 ± 0.16 a

1.25 ± 0.05 a

1.34 ± 0.19 a

Arginine

28.11 ± 0.18 d

26.46 ± 0.16 c

22.34 ± 0.65 b

5.43 ± 1.03 a

4.14 ± 0.30 a

5.14 ± 0.65 a

Alanine

7.08 ± 0.41 b

15.82 ± 1.10 c

25.16 ± 0.63 d

2.74 ± 0.50 a

4.28 ± 0.29 a

8.65 ± 0.79 b

Tyrosine

4.33 ± 0.08 a

5.61 ± 0.32 b

5.84 ± 0.45 b

n. d.

n. d.

n. d.

Valine

7.82 ± 0.22 b

9.01 ± 0.54 c

11.73 ±0.61 d

0.57 ± 0.11 a

0.84 ± 0.05 a

1.39 ± 0.30 a

Methionine

1.62 ± 1.59 a

1.61 ± 1.57 a

0.64 ± 1.26 a

0.93 ± 0.11 a

1.17 ± 0.06 a

0.90 ± 0.00 a

Tryptophan

8.38 ± 0.23 b

15.71 ± 0.39 c

7.73 ± 0.57 b

0.65 ± 0.16 a

1.08 ± 0.14 a

1.08 ± 0.14 a

Phenylalanine

8.71 ± 0.06 c

15.46 ± 0.37 d

8.49 ± 0.43 c

1.83 ± 0.23 a

2.58 ± 0.14 b

2.26 ± 0.04 ab

Isoleucine

3.08 ± 0.09 c

4.14 ± 0.23 d

4.84 ± 0.22 e

0.14 ± 0.14 a

0.24 ± 0.02 ab

0.58 ± 0.10 b

Leucine

2.66 ± 0.19 b

5.00 ± 0.35 d

3.48 ± 0.53 c

0.08 ± 0.15 a

0.51 ± 0.04 a

0.45 ± 0.07 a

Lysine

6.99 ± 0.32 c

8.96 ± 0.35 d

11.51 ± 1.10 e

1.38 ± 0.21 a

1.24 ± 0.09 a

3.42 ± 0.58 b

Proline Total

3.47 ± 1.67 a

8.13 ± 0.21 b

8.46 ± 0.32 b

2.40 ± 0.27 a

2.83 ± 0.40 a

2.22 ± 0.36 a

625.07 ± 8.77 c

643.66 ± 10.26 c

698.14±15.31 d

68.55 ± 12.03 a

75.90 ± 2.54 a

106.28 ± 13.13 b

n. d. = not detected Values with different letters in a same row are significantly different (p < 0.05) 24


Page 25 of 28


Table 3. Total amino acids content (g/100 g FFDM) of unroasted seeds of different varieties Amino acids

BJ

BJO

RS

Aspartate

2.21 ± 0.04 c

2.07 ± 0.03 b

1.98 ± 0.03 a

Glutamate

6.39 ± 0.10 c

5.96 ± 0.05 b

4.73 ± 0.06 a

Serine

1.61 ± 0.05 c

1.51 ± 0.04 b

1.30 ± 0.02 a

Histidine

1.19 ± 0.02 c

1.09 ± 0.02 b

0.86 ± 0.02 a

Glycine

2.06 ± 0.04 c

1.94 ± 0.03 b

1.66 ± 0.03 a

Threonine

1.68 ± 0.02 c

1.59 ± 0.02 b

1.45 ± 0.02 a

Arginine

2.77 ± 0.04 c

2.59 ± 0.04 b

1.94 ± 0.03 a

Alanine

1.67 ± 0.03 c

1.57 ± 0.01 b

1.38 ± 0.02 a

Tyrosine

1.17 ± 0.03 c

1.08 ± 0.02 b

1.00 ± 0.02 a

Valine

1.84 ± 0.03 b

1.86 ± 0.02 b

1.61 ± 0.03 a

Methionine

0.55 ± 0.02 b

0.57 ± 0.05 b

0.46 ± 0.01 a

Tryptophan

0.43 ± 0.03 ab

0.45 ± 0.03 b

0.37 ± 0.04 a

Phenylalanine

1.68 ± 0.04 b

1.61 ± 0.04 b

1.32 ± 0.04 a

Isoleucine

1.69 ± 0.03 c

1.60 ± 0.02 b

1.37 ± 0.03 a

Leucine

2.71 ± 0.05 c

2.58 ± 0.05 b

2.18 ± 0.04 a

Lysine

2.25 ± 0.08 b

2.21 ± 0.07 b

1.94 ± 0.06 a

Proline

2.72 ± 0.03 c

2.57 ± 0.04 b

2.05 ± 0.03 a

Total

34.62 ± 0.59 c

32.85 ± 0.49 b

27.60 ± 0.47 a

Values with different letters in a same row are significantly different (p < 0.05)

25



Page 26 of 28

Table 4. Changes in the sugar composition (mg/g FFDM) in the seed after 10 min of roasting of different varieties roasting time (min)

fructose

glucose

sucrose

BJ

unroasted

6.70 ± 0.29 d

46.60 ± 1.92 c

51.70 ± 1.62 b

BJO

unroasted

3.80 ± 0.18 b

48.56 ± 2.58 c

62.77 ± 1.37 c

RS

unroasted

3.94 ± 0.27 b

12.43 ± 0.94 b

70.42 ± 2.27 d

BJ

10

5.99 ± 0.22 cd

3.51 ± 0.12 a

33.37 ± 2.85 a

BJO

10

5.16 ± 0.84 c

4.49 ± 0.48 a

48.95 ± 3.04 b

RS

10

1.07 ± 0.03 a

1.44 ± 0.25 a

84.74 ± 5.15 e

Varieties

Values with different letters in a same column are significantly different (p < 0.05)

26


Page 27 of 28


Table 5. Fatty acids composition of oil (g/100g oil) from different mustard and rapeseed varieties Fatty acid

BJ

BJO

RS

16:0

2.6

2.5

4.4

16:1

0.1

0.1

0.2

18:0

1.1

1.3

1.1

18:1

17.8

18.8

53.9

18:2

18.1

19.0

19.8

20:0

1.1

1.2

1.1

20:1

8.4

8.2

0.3

18:3

15.4

13.9

9.7

20:2

1.0

0.9

n. d.

22:0

0.2

0.3

n. d.

22:1

20.6

21.3

n. d.

24:1

1.2

1.2

n. d.

n. d. = not detected

27



Page 28 of 28

Table of contents graphics Total tocopherol (µg/g oil)

600 500 400 300 200

Juncea oriental Rapeseed

100 0 0

20

40

60

roasting time (min)

80

Canolol (µg/g oil)

900 800 700 600 500 400 300 200 100 0

Juncea oriental Rapeseed

0

20

40

60

80

roasting time (min)

28


Effect of Seed Roasting on Canolol, Tocopherol, and Phospholipid

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